The Green Flag is used to start the race, or to resume competition after a full course yellow or black flag. Some sanctioning bodies, notably CART, requires that the green be displayed at the next corner station after a yellow flag, so the drivers know they may resume racing.

The Yellow Flag signals a hazard, generally another car, but could also be some form of debris ahead large enough to signficantly damage a car. One time at Mid Ohio Sports Car Course, it was used because a sheep had escaped a nearby farm and wandered onto the backstraight. The session was stopped and tiltbedtow truck called in to secure the sheep after it was captured.

A Stationary Yellow is displayed when an incident occurs that is not on the track. This may include an emergency vehicle that has pulled off the track. There is no passing until after the incident., and drivers are expected to be prepared to change their racing line. Most don't, knowing the track is supposed to be clear they head through at full speed. They stay fast because they don't want to give their competitors an advantage when green flag racing resumes after the incident. But their heads do swivel, searching for the reason for the yellow, and most are cautious until they see the incident for themselves.

The Waving Yellow is different. The drivers, well the bright ones, do slow down. They know that when the yellow is waved there is something big on track ahead of the them. In fact, the waving yellow covers everything a wheel on track to the entire track blocked, with someone on their roof spinning like a department store door. A waving yellow is a very serious thing. The GCR says a yellow signals "extreme danger". Drivers are expected to slow down and be prepared to stop entirely.

Sometimes a station that is waving yellow, or has emergency vehicles may request a backup yellow from the preceding corner station. Then there is no passing between the two stations. This makes it easier to control the cars passing a serious problem.

ADouble Yellow signals a Full Course Yellow. All stations and start will display two yellow flags, slightly separated. Normally, this is used on the pace lap -- or laps- of a race. No passing is permitted anywhere, though a slower car may wave a faster car by. The station where the incident is may either display a waving yellow, or one yellow, if the situation merits. The flag differential indicates to the drivers the location of the incident, and that they should be especially cautious.

Normally a double yellow is only used when there is a serious incident, or multiple incidents on course, that cannot be safely cleared under local yellows. All pace laps take place under a double yellow, though the last one or two statons before start may not display a yellow. Some sanctioning bodies accomplish the same thing with a single yellow at each station, but putting up two gets the information across a little quicker.

A Red Flag is a very serious thing. In three years of flagging, I've thrown the red only once. That occasion involved lots of ambulances and the involved corner completely obscured by dust smoke. As a driver, the only time I've ever seen one was at my first driver's school, and that was to sensitize us students. Red Flag situations are so serious that many divisions do not allow the word red to be used on the phone net at all. A red flag is ordered by the steward when a situation has come about that makes further racing impossible, and the track impassable. If you see one, someone's life is at stake.

When a Red Flag is ordered, it is displayed at all stations. all cars are to stop immediately right where they are, and not move until instructed by their friendly neighborhood corner worker, (in Europe a turn marshall). After which they are told to head to pit lane.

For races supervised by the Champ Car World Series, the Red Flag is used like the Black Flag

Black Flag situations are more common, but can be quite extreme. I remember one where a car was spinning on its top, center track at Oak Tree bend at Nelson's Ledges Road Course, and a cloud of dust making visibility impossible. When a Black Flag is displayed at all stations, there is an incident on track that must be cleared immediately and cannot be safely cleared wih cars on course. Like the upside down rotating honda. Upon seeing the Black flag, all cars are supposed to drive at slow speed to the pits, where they will await further instructions.

A disciplinary Black Flag may be shown to a driver who has committed a significant no-no of one type or another. It is displayed at the Black Flag Station, a station which is designated in the supplemental regulations, and Start. The flag is displayed to the driver, along with a number indicating who needs to have a chat with the Steward. An unhappy Steward, ready to instruct you in the error of your ways. If the Black Flag is furled, then it is a warning, Black flags are sometimes missed, but woe be it to any driver who does not come in after two laps.

The Mechanical Black Flag, or Meatball flag consists of a black flag, with an orange ball in the center, which gives the flag its nickname. The flag is displayed at the Black Flag Station and start, along with the number. Drivers recieving their meatball are expected to report to their pit, because something wrong has been observed in their car. A wide array of safety and mechanical problems may lead to a meat ball, the most common being fluid dumping. This may annoy the driver, but I have personally been part of a meatball that prevented a blown engine due to oil loss.

The Surface, or Slippery flag consists of alternating bands of yellow and orange, and is displayed to warn drivers that there is something on the tracks surface they need to be concerned about about. This may be oil, but can also be loose grass, stones are a sharp object capable of puncturing a tire. Anything that might lead to loss of control may lead to the flag being displayed. The call on displaying one is difficult, because if overused drivers may ignore it when it is really needed. The surface flag is often displayed for one lap of the entire field, so as to warn the dirvers of a condition and then dropped. Drivers seeing the flag are expected to look for the problem themselves, though the corner workers may point to the spot..

The White Flag signals there is an emergency or slow moving vehicle on course, often a disabled race car. It is displayed for two stations behind the slow moving vehicle, and may be displayed with other flags, such as yellow and Surface. Often Corner workers become very creative to display all the flags requried for a given incident. A white flag is also displayed during the first warmup lap for each race group on a race weekend. This points out the corner stations to drivers, some of whom may not have raced at the course before.

The Blue Flag is sometimes misnamed the passing flag. The flag does not instruct another driver to move over, it advises him or her that a faster car is approaching them from behind. In all cases, the GCR is clear that the overtaking car has the responsibility for making a safe pass.

Blue Flagging is a challenge, something of an art, and the exact uses of it are debated among flaggers. It is expected to be shown when a leader is overtaking lapped traffic, or when the pass is not for position. However, many use blue flag when the pass is for position, provided the overtaking driver is considerably faster, such as when a very fast car starts at the back for some reason. Drivers are competitive, so flaggers are taught to sell the flag. But a few badly chosen blues may lead some drivers to ignore them.

The Checkered Flag is displayed at the end of each race, qualifying and practice session. It is black and white in a chessboard pattern and is the one thing a driver wants most to see, particularly if he or she is the first person to see it. For a practice session, the Black Flag station may also display the checker, to clear the course more quickly.

Some flags above are not used by other sanctioning bodies. CART does not use the Meatball, and AMA and Go kart racers don't use the blue, or the white.

Both AMA motorcylists and karts do use the Ambulance Flag, which is white with a red cross in the middle. This flag is given two stations back when an ambulance is on course. It gets their attention, and quickly as slamming into the back of an ambulance hurts real bad.

Motorcycle Racers use the Pickle Flag , which is oversized, and green with black stripes. It is only used when there is oil on the track. Cyclists do slow down for the pickle flag, as oil leads to painful spills